Solar panel efficiency has been the talk of town since quite a few years as manufacturers have always liked to advertise their products based on it. Solar panels from different manufacturers have been compared keeping the panel efficiency in the centre. But, does the solar panel efficiency really matter? Is it the one key factor you should really be worried about? You will find out the fact and will be surprised to know that the panel efficiency is important but not as important as it looks!
What is solar panel efficiency?
Solar panel efficiency, in simple words, can be explained as a conversion ratio of sunlight to electricity from certain area. It should be noted that solar panel efficiency is different than solar cell efficiency. According to research in UNSW Australia, the silicon cell has a record breaking efficiency of 34.5% back in May 2016. However, it is just a prototype and can take long time to get commercialised.
Although the solar panel efficiency is not as alluring as solar cell efficiency, it is quite often used by marketers as a key factor in designing solar photovoltaic systems. Solar panels are manufactured using 50 to 100 solar cells depending on the size of the panel. The combined output of all used solar cells is called solar panel efficiency.
Significant increase in the manufacturing cost perhaps is the reason of denial for solar panel manufacturers to adopt the more efficient cell technology in mass production. Increase in manufacturing cost eventually leads the increase in solar panels and that is certainly going in wrong direction for pricing. Therefore, solar panels have failed to show significant improvement in efficiency over the last decade.
How to calculate solar panel efficiency?
1000 watts of a sunlight falling on solar panel generates 200 watts, that’s 20% efficiency.
The maximum output can be derived when solar panel takes 1000 watts of solar irradiance at a surface temperature of 25o C and air mass of 1.5G. These are Standard Test Conditions (STC) under which solar panel manufacturers observe the performance of solar panels and evaluates the efficiency.
How are roof space and efficiency related?
Let’s take an example. A 2kW solar PV system can produce about 8-10 units a day in India and only requires 20 square meter shadow free area. Also, let us assume enough space available for installation of solar PV system.
A solar PV system installer has two options.
Install 7 panels of 300 watts
Install 8 panels of 250 watts
In both cases the output will remain almost same under normal cases, however, adding one more panel with less efficiency would be an economically wise decision over going for a selection of 300 watts panels. This is because the price of 300 watts panels is certainly higher than that of 250 watts panels. Therefore, the efficiency of solar panel would not bother much if the space is not at all the constraint.
Can less efficient solar panels get you a better deal?
The efficiency of solar panels has nothing to do with performance and reliability and everything to do with its manufacturing standards. The more efficient panel will certainly get you more output but at an increment in cost. On the other hand, the panel with a little lesser efficiency can save you money. This really counts when the solar photovoltaic system size is bigger and space is not a constraint.
The cost of electricity produced should determine the value of solar panel. As mentioned above, adding one panel can be a wise decision than paying premium for better efficiency panels. One should instead, focus on the manufacturer brand, performance, and warranty aspects of the panel.
In a nutshell, having a least concern about solar panel efficiency one can rather find a middle ground for price, performance and reliability and avoid products that are towards the bottom end of the price as well as efficiency.
